1. Field of the Invention
The present invention relates generally to the field of telecommunications and, more specifically to a method and apparatus for providing dynamic allocation of conferencing resources in an expandable telecommunications switching system.
2. Background Information
A competitive telecommunication system must be capable of providing a wide variety of telecommunications services. For example, subscribers may request services such as voice processing services, call waiting, caller identification and call forwarding. In the commercial context, one of the most desirable services is that of conferencing. Conferencing refers to the ability of three or more callers each using a separate telephone set and often located at remote locations from each other, to participate in a single telephone call simultaneously. In addition, there is an ever-expanding need for conferencing services, which can accommodate reasonably large conferences of, for example, about 30 participants. In addition, there is a need for a conferencing service, which can adapt dynamically to a change in the conference size while the conference is in progress.
In addition, the advantage of an expandable telecommunication system is that additional capacity for handling a greater amount of telecommunications, or additional components, which can provide new services, may be added to the system while the system is in operation. This is often referred to as “hot-plugging” components. At times, if the configuration of a telecommunication system is changed, this can affect the communications that are then in progress. This is because the timing and control in a high-speed telecommunications system is critical and any change in the system could result in dropped time slots of voice information or, ultimately, to dropped calls. This is also true of conferencing. The input signals of voice information from the conferees or the conferenced output could be affected should a change in the system configuration be made. Thus, there is a need for a system which provides conferencing services that will support a conference in progress and minimizes the risk that an entire conference is dropped or participants in the conference are purged even when components are hot-plugged into the system.
Originally, conferencing systems had interfaced with a conventional computer-controlled digital switching matrix within a Private Branch Exchange (PBX) switch or a public switching system that provided a circuit switching function. More recently, it has been known to provide conferencing in a high-speed digital communications network that includes a plurality of switching nodes with each node including its own nodal switch. This type of system is described in commonly-owned U.S. Pat. No. 5,920,546 (Hebert et al.) for a METHOD AND APPARATUS FOR CONFERENCING IN AN EXPANDABLE TELECOMMUNICATIONS SYSTEM, which is presently incorporated herein by reference in its entirety.
In accordance with that system, at least one node in the system (e.g., a conferencing node) contains a digital signal processing (“DSP”) circuit capable of performing a conferencing operation on the voice information of the conferees. More specifically, the DSP circuitry executes a conferencing function on the voice information by operating on it using, for example, a conferencing algorithm that often includes summing together the channels of voice information from each conferee. As is typical in the industry, after summing all of the voice data, the conference processor typically subtracts each conferee's data from the summed total intended for that conferee. This is done in order to minimize echo effects and improve system stability. The DSP circuit executes this conferencing function on the voice information and then outputs a different instance of conferenced voice information for each conferee. Each instance of conferenced voice information is then transmitted to the corresponding conferee. Sometimes, this may occur within a single node. In other cases, the conferencing node may be a remote node, which is located elsewhere in the network, and is not interfaced with any one of the conferees.
When conferencing resources in a DSP are located, the voice information from each node interfaced with a conferee is addressed and transmitted to the conferencing node, over the inter-nodal network. The DSP circuitry in the conferencing node performs the conferencing algorithm and then places the instances of conferenced voice information on an internal bus located in the conferencing node. A data transmitter in the nodal switch that is preferably linked with the bus then receives the instances of conferenced voice information. Next, the conferencing node may formulate a packet or packets containing the instances of conferenced voice information for transmission via its data transmitter over the network. Specifically, each instance of conferenced voice data may be packetized, addressed and transmitted via a time slot (or channel) assigned to the conference according to instructions from the system. The time slots of conference voice data are transmitted to the programmable switching node interfaced with the corresponding conference participants. Each programmable switching node, upon receipt of the packet or packets then captures the instance of conferenced voice information ear marked for that participant via its own data receiver and switches the information to the participant. Further details of the routing of this information may be found in the '546 patent.
Despite its utility in forming a conference that has a high quality voice signal output, the conferencing technique described in the '546 patent does not fully allow for the further capacity to accommodate conferences that may dynamically grow or shrink. In addition, there is a further need for a conferencing system that is adaptable for handling conferences in progress even when certain components (such as a T-1 line card) are added into the system while the system is in operation. This need is particularly great with larger conferences of about 20–30 participants.